When designing a circuit, considerations must be given to the fact a microwave monolithic integrated circuit is greatly affected by the properties of a package parasitic component as the frequency range thereof is relatively high. In particular, as an interference effect between the elements within the circuit which occurs through the ground terminal affects the stability and the performance of the circuit, it is important to analyze the interference effect exactly.
When representing its parasitic component using an equivalent circuit of a conventional package ground terminal paddle, an individual consideration is given to all the possible impedance components between the terminals attached to the gold wire that is down-bonded from a chip. Accordingly, if the number of gold wires to which the paddle is down-bonded is many, the equivalent circuit of the ground terminal paddle is complicated and accordingly it is difficult to find the values of all the impedance components thereof, thereby requiring much efforts and time in designing a circuit.
When the number of the gold wire which is down-bonded at package paddle is many, the impedance between each down-bonded terminal has different values according to the shape of the paddle and the distribution of the terminal. The interference effect through the down-bonded terminals, which affects the stability and the performance of the circuit is biggest between the neighboring terminals positioned farthest from a ground via hole because the magnitude of impedance between the down-bonded terminals is small and that between the down-bonded terminal and the ground via hole is large. Considering that the impedance component to cause this largest interference is seen between all the terminals, the deterioration of the performance in the chip characteristic due to the interference through the ground terminal can be avoided since the chip characteristic can be simulated in a worst environment. However, a conventional equivalent circuit has a drawback in that it is not capable of reducing its complexity because it is designed to have the impedance component among all the down-bonded terminals and the ground via ones.